A delta motor system typically includes a delta motor, a three phase power source and a motor controller. During start up, delta motors often experience potentially damaging high inrush currents and starting torques. This can adversely effect the performance of the motor drive and increase general wear and tear leading to higher maintenance costs. In addition, current peaks during motor startup can also cause voltage disturbances in the power supply.
Motor controllers are typically used to restrict the motor torque and reduce the high starting currents by controlling the application of voltage from the three phase power source to the delta motor. The motor controller generally includes a set of three control switches that are connected between the line voltage terminals of the three phase power source and each of the windings of the delta motor. The motor controller regulates the voltage from the three phase power source to the delta motor by selectively opening and closing the three control switches. The proper operation of the delta motor is dependent on the proper regulation of the control switches.
The motor controller's internal timing mechanisms are specifically designed to regulate the application of specific line voltages from the three phase power source to specific delta motor windings based on a predesignated wiring configuration. Conventional electrical leads are typically used to connect the delta motor windings to the control switches and to the line voltage terminals. Since the electrical leads providing connection to the delta motor terminals are not always clearly marked, mistakes in wiring the delta motor system are not uncommon.
A common wiring error where the two leads providing connection to a single winding are electrically coupled to a single line voltage terminal while the other two windings are connected in parallel across the remaining two line voltages terminals, is known as a single dead ended winding wiring configuration. In this configuration, the dead ended winding does not have any current flowing through it while the other two windings are subjected to lower motor torque and significantly higher current conditions. The lower motor torque in combination with the higher operating current can potentially damage both the delta motor and the motor controller.
Clearly it would be desirable to use a motor controller that automatically detects a single dead ended winding configuration so that the faulty wiring can be corrected prior to subjecting the delta motor and motor controller to the potentially damaging combination of low motor torque and high operating currents. The present invention seeks to achieve these objectives.